


Servitude

by HibernalBeast



Category: Undertale (Video Game)
Genre: Alternate Universe - Swapfell, Blindfolds, Cunnilingus, Double Penetration, I'm Bad At Tagging, Light BDSM, Mating Cycles/In Heat, Multi, Polyamory, Shameless Smut, Swapfell Papyrus - Freeform, Swapfell Sans, Vaginal Fingering
Language: English
Status: Completed
Published: 2018-06-04
Updated: 2018-06-04
Packaged: 2019-05-18 04:14:00
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 5,074
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/14845508
Author URL: https://archiveofourown.org/users/HibernalBeast/pseuds/HibernalBeast
Summary: For 7 months you have been in a relationship with Rus. Things are going great between you two but his brother Sans, is a constant pain in the ass. Or is he?I had an idea. So I had to write said idea! I hope you enjoy, please do leave a comment, if you got any feedback ;)





	Servitude

 

For the last 7 months you had been the target from relentless harassment. From no other than your own boyfriend's brother. For all intentions and purposes, he truly was a monster – literally. 

It had been few years since the monsters came up from Mt. Ebot and there had been alot of discourse and problems at first, the adjustment had been a rough one and slow progress. From the get-go you had been pro-monster. For your sensibilities, their story was one of heartbrake and injustice. You met Rus in a monster run bar, Grillby's, where you had begun to be somewhat of an regular. Incidentally, he too was there always, sitting slouched at the bar, floofy hood pulled over his skull and seemingly lost in his thoughts. 

Something about him just pulled at your heartstrings especially, so striking up a conversation was inevitable. At first he seemed surprised that you even noticed him, then he seemed suspicious and it took a long time to actually get him to open up to you a little bit, to get a slight friendship to blossom. The challenge to befriend him was something that sparked most of your interest, but after long nights with him, talking about everything and nothing, you noticed you were genuinely interested in the skeleton monster. 

After a very drunken night, when you finally confessed your feelings to him, he surprised you yet again and pulled you close, kissing you with foreign fervor that you would have never expected from such a lazy guy. Even if there was much more to him, than him being the easygoing dude he outwardly portrayed. 

Few weeks after that you actually got to meet his brother.. Sans. 

Rus hadn't talked about him much and after meeting him you did not wonder why for a second. You also wanted to slap Rus for not mentioning _how_ he was. He was the single most aggravating, haughty and pompous person you had ever had the displeasure to come across. Even your holier than thou aunt didn't come even close, and that was saying something! 

The way Sans talked to you, and more importantly, to Rus, made your hide itch and heart fill with visions of violence and you weren't that violent of a person. You just had very strong opinions on how people AND monsters should be treated, even more importantly, how family should be treated.  
The first altercation came so fast that it felt like a slap against your face. You just couldn't keep your trap shut when Sans called Rus _”Mutt”_ and yelled at him for missplacing something totally inconsiquential. 

You couldn't listen to it, or watch Rus just standing there looking like a dog that had been just hit with a leash while Sans raged around him, aggressively pointing with his gloved hands and swishing his riding crop, that the weirdo always carried around. You launched yourself between them, pushing Sans away from the both of you and snarling at him like a wild animal. 

_”Don't talk to him like that! What the fuck is wrong with you?!”_

The silence that had fell in the room was frightening. Rus was almost vibrating at your back, but so was Sans. The shorter skeleton monster was staring at you with widened eyesockets, wine red eyelights constricting into tiny pinpricks and then bursting into a wild flame. The growl he emitted did strange things to you. You never could have imagined being afraid of a monster but by gods you were. But your stubborn streak took over like a buried instinct and to your best abilities, you growled back, your blunt human teeth bared in a similar, if not a lot less intimidating snarl that Sans was sporting. 

Things were escalating so quickly that before anything else happened, Rus did the only probably intelligent thing and teleported you two away, to the safety of your home. 

You were a wreck after the adrenalin in your system started to wane. You were terrified, crying like a baby, but Rus just held you close in his arms and petted your head, whispering how fucking proud he was, how _astonished_ he was, that you had stood against Sans for him. The same night he told you that anyone who had ever done that kind of thing for him had been Sans. It was hard to believe from their interractions. To you it seemed that Sans didn't like or appreciate his brother one bit, but Rus reassured you, that that wasn't the case. 

That was also the first night that he opened up about the life beneath the mountain for real. Up until that point it had been a subject that he had quickly diverted all talk from, to something else. After hearing about their life, you didn't wonder at all why. 

You still couldn't understand why Sans had to treat him like he did, because showing weakness wasn't something that had such momentous consequences topside. Rus of course saw it differently. Monsters were still harassed and there were hategroups that targeted them and from his perspective, things certainly weren't as safe as you might have thought. It surely was something you felt ashamed for. Your life had been easy and sheltered compared to his and his past wasn't something that you could just internalize in few nights. 

After, you were terribly worried that Sans would jump you the moment he saw you and just rip you to pieces but Rus promised he wouldn't. It didn't make you any less nervous to see him the next time. Maybe he would just rip you a new one, instead of, you know, ripping you to shreds, limb by limb. 

That didn't happen, of course, much to your relief. Instead, the next time you ran into him, in the quiet of the brothers' apartment at 3 a.m when you got up to get water he just watched you with narrowed sockets, a nasty spark in his eyelights. He made you so nervous you dropped the glass of water and cut your hand trying to pick up the shards. The bastard just stood there, tapping his foot and staring holes through you and _smirking_. It took all of your willpower to keep your temperament down and not blow up in his face. 

He surely seemed to bring out that side out of you, with a ease that made your head spin. You had always thought yourself as a quite mellow person but he could make your blood boil, without saying a word. 

After that, he made sure to try and aggravate you every fucking chance he got and there were plenty opportune times to do that.  
Ordering you around like you were a maid in their house, making you look stupid and weak and useless and just.. demeaning your mere existence like it was a personal crusade to him – it most likely was. 

Rus seemed nonplussed by it, not intervening, since it wasn't something that he ever did, stand up to his brother that is. He seemed just as interested in how you reacted as Sans and sometimes you really needed a moment to gather yourself so you didn't end up releasing your pent up anger at him. It wouldn't have been fair. You understood that the situation must have been fascinating to him, since he had never experienced something like it before. He had told you that the majority of monsters were terrified of Sans in the Underground and would have never imagined backtalking to him. 

So Sans was used to being treated like a spoiled kid and some backtalking was long due, in your honest opinion. Since neither Sans or Rus seemed to actually _do_ anything that drastic about you being mouthy, you took the bait and fired back at Sans. Refusing to step down and let him boss you and Rus around. The bickering back and forth was tiring, but every time your jab at Sans landed like you intended, making his expression change subtly to outrage, you felt like you won a fighting match and it became someway addicting. 

Besides, he started it. 

Okay, yes that was an incredibly childish way of viewing the situation, but dammit, you were invested! You wouldn't let him steamroll you down to the ground. 

Months of the same ilk and it was a entablished behaviour between you two, him trying to get under your skin and you trying to get to his marrow. You still hated his non-existant guts, but it was also something that you were used to about him. It was just the way he was, with everyone, more or less.  
When it started to take a turn for something that could have been interpreted as teasing, you started to be a little weirded out. Maybe he had just upped the ante, trying new ways to get you to react and react you did. You couldn't really help it.

He was being even more demeaning, if possible, and it made you really brake a sweat that you didn't even want to understand. Leaning close to you, too close for comfort, voice low and dare you say, even sultry, whispering next to your ear. Seemingly innocent little brushes of his hand against various parts of your body that made shivers go down your spine, the creepy little shit. A sparkle in his eye that suspiciously looked like he was dressing you down in his minds eye. You didn't even know how to handle that or how to talk about it to Rus, since he always did it when he either wasn't near or didn't see it. It all made you incredibly flustered and most times you just found yourself in loss for words. Sans seemed delighted at the fact. 

All that had escalated for 7 months, but you cared about Rus too much to let him run you off. Sans could suck a fat one and keep trying to make you loose interest all he wanted, it wasn't going to happen! 

That weekend Sans had made plans to leave the apartment to visit his friend, Alphys and Rus and you had made plans to lay around in his place, since it was sans Sans. Perfect, in your opinion. Rus had been hinting at maybe trying something a little bit different and it had certainly sparked your interest. Usually you were the one to initiate any sexual situations, since he truly did have a lazy streak and you honestly didn't mind that. You liked control, you couldn't lie about that. But for him to take that step and propose something.. well. You wouldn't say no to that. 

You arrived at their house at 9 pm, excited and a little bit anxious, ready to see what the ”something different” was going to be. With Rus, you weren't exactly sure what he had meant. It could have been anything, he did surprise you from time to time. When he opened the door, he seemed very nervous. Sweating up a storm, fidgeting and eyelights a little shifty. What ever this was going to be, he clearly was excited about it too. His demeanor made you nervous too and you smiled, taking his bony hand in your own.

”Come on big guy. Show me what got you in all knots.” 

The hacking cough that burst out of his mouth, with a flaring flush of burnt orange made you giggle. He was really acting weird.

”Well Darlin', since ya usually do all the work.. ” He pulled you gently to his room and your eyes widened. 

Well, well, well. Your gaze roamed the room, landing on his bed. There was a set of handcuffs, some rope and a blindfold, neatly laid on the covers. It wasn't like you hadn't done any of this shit before with impromptu equipment, but this was all brand new stuff. 

”You.. wanna tie me down?” Your astonished tone made him smirk wide, golden canines glinting in the low light of the room. Only an old small lamp on his messy desk illuminated the room.

”Yeah.. ya okay with that?” 

You couldn't really trust your voice, even the thought got you going, so you just turned to him, nodding your head with enthusiasm. He answered with a low chuckle that you loved, the loving look in his eyes shooting right to your core.

He started to dress you down, going so slow that you wanted to hurry him already but you did your best to let him go at his own pace. He had made sure to make you know all these months that he loved each and every inch of your body and him getting to do this to you was something that you knew he enjoyed. 

After he had undressed you, he blindfolded you while he was distracting you with kissing, making you jolt with surprise. Loosing one of your most important senses made you a little scared, but you couldn't deny that you liked it too.

Next came the ties – he cuffed you to the metallic ends of his bed, using the rope to tie your legs – with legs bent and pretty much useless. You would have thought he'd tie you down to the other end of his bed, but that wasn't the case. Still, you were effectively disabled from moving around much, laying on his bed, goosebumps rising up on your skin as you were already lightly panting.

”Ahh, Darlin', ya look absolutely gorgeous, like a tasty little treat..” Rus' low murmuring made your face burn and you whined. You had always loved his deep voice and now that you were this _helpless_ it affected you even more.

”Now.. don't freak out, but I gotta ask ya somethin'.” 

But you did freak out, your heart starting to hammer harder in your chest, cold shivers going down your spine. What the fuck did he mean with that? What was that tone of voice, it was so .. strange. Something you hadn't heard from him before and it made you nervous and scared. You wanted to see his expression, but the blindfold was drowning you in a darkness that the weak light of the lamp did not penetrate. 

”Wh..what? What's going on, Rus??” your voice rose to a indignified squeeke at the end, something weird was going on and you didn't know if you liked it at all.

”Ya see.. We need yer help with something.” 

_We_? What? What the hell was going on? You could feel sweat trickling down your neck.

”Uhm.. excuse me??” was your highly intelligent answer.

”Yeah.. I uhh, knew ya'd freak out so I had ta tie ya down for this.. ” You could hear Rus scratching his skull, probably a little bit sheepish, you could hear it in his voice clearly. ”But ya know. I know ya don't really hate my bro, even if ya frequently say so. An' I know he doesn't hate ya.” 

”...” 

You couldn't even answer that. Where was he going with this? You'd thought you wouldn't be able to be even more nervous but jesus christ, you certainly were. For some strange reason you felt like your sins were crawling on your back.

”.. Rus, what the hell are you talking about?” you managed after a while.

”Sans went into heat this mornin' an' it's bad.. Ya know.. he's been gearing up to let ya know how he feels about ya an' .. we both know ya have some feelings too. Ya ain't that good covering them as ya might think. Yer soul.. it resonates with both of us, Darlin'.” 

Your mind was going thousand miles per minute and you tried to squirm around a bit, but it was useless. You couldn't escape this. You probably looked incredibly stupid, mouth opening and closing like a fish trying to breathe on land, face flushed dark red and sweating up a storm. A flare of anger made you huff irritably but you still couldn't get any word out.

No.. you didn't hate Sans. He.. it was complicated. For fucks sake they were brothers?! Wasn't Rus angry? He didn't sound angry at all, if anything he sounded a little bit amused. He sounded sure, this wasn't speculation about your feelings at all. And heat? Yeah you knew what that was and the thought was intimidating. Rus had not gone into heat while you had been a thing, and he said that he rarely did, because he was too lazy. But Sans. Lazy wasn't something that he would have ever been caught to be described as. He was a malicious ball of energy.

And souls? You knew a little bit about them, but not alot. They were important to monster, but all in all, the concept of souls, even if it wasn't exactly knew to humans, the fact that they were real, actual thing was. You certainly had never seen your own soul, but you could damn well feel it inside you now, like it was being called to react. Called forth. Making you face this as forcefully as Rus was. 

”I.. I.. but you're bothers? I'm.. uh..” 

**”I'm not hearing a no.”**

You screamed.

When the hell had Sans come into the room?? Fuck, he was seeing you butt naked, TIED DOWN on Rus' bed. 

**”Music to my ears. Now, to the point. Us being brothers? Yeah, and so what? Polyamory isn't exactly a foreign concept to us monsters and I happen to know it isn't that to you humans either.”**

Rus chuckled once more, now more near to you and you tried your best to shield yourself from Sans' gaze but it was impossible. You could also hear that he sounded.. not fine. His voice was rough, almost half growl all the time and winded, like he had just ran a marathon. Yup, he definitely was panting. Closer now. Your legs twitched with the knee-jerk instinct to bolt, but you couldn't. 

You also couldn't deny the deep ache his rough voice was sending to your core, your stomach lurching with a insane concoction of emotions ranging so far wide you could hardly keep pace. 

”Ah.. a.. I, don't you despise humans? Despise me?” you winced at the way you sounded so tiny, so unconfident. And how you sounded close to just moaning, way too excited.

Sans' laugh was much closer now, making you tremble uselessly on the bed. Usually his laugh was as aggravating as his personality, but it was much more smooth this time, completely new from him. Your body's reaction was instantaneous, the arousal almost painful. You were mortified, certain beyond any doubt that both of the monsters noticed.

You jolted again, when you felt Rus sliding next to you, wrangling you so that he could slip under you, where he could hold your prone body against his. You felt his ecto-cock pressing against your back and sighed a little, feeling simultaneously more safe and nervous for what was a about to happen. 

**”Wrong, human. Do you think that I would have let you be with my brother if I despised you? Certainly not. You made an impression on me, and continued to make one, after all. And now you WILL serve me.”** His confident tone of voice made your heart do flip flops around your chest and you actually whined, making him laugh that smooth, satisfied laugh again. 

Christ you really were a freak. But no one was complaning. 

”Just relax, Darlin' ya can trust us.” Rus whispered to your ear, ruffling the loose hairs on your neck, chills coursing down your back again. 

You couldn't believe you were gonna submit to them like this but here you were.. not saying no. You had never been one for submission with any of your previous human partners, but gues it just really did take a certain partner for that and the way Sans ordered you to serve him made you weak in the knees, not even thinking about declining. You certainly were finding alot of new things about yourself and them tonight.

Feeling Sans' rough, bony hands land on your ankles and sliding up to your knees to push your legs apart more made you gasp, pushing your head against Rus' clavicle. His bones were almost uncomfortably warm, most likely from his heat. Restrained like this the feeling of his battle hardened hands was hightened and you couldn't deny liking it.

You wanted to see his face, his eyes, how he must have looked staring you down, your already wet pussy. For a moment you were sad for the blindfold, but his ragged breathing and the slowly uttered **”..fuck..”** painted you a good enough picture in your mind. 

His fingers slid towards your slit, gliding easily over your labia to your clit and you moaned, the feeling criminally good for such a simple touch. 

**”Mmmmh, so wet already, like you are supposed to be.”**

A snarky answer bubbled up on your lips but it turned to strangled moan, as he plunged two fingers inside your pussy, making his point at you being dripping already.

He started up a deep, but tortuously slow pace, bottoming his fingers inside you and you could feel his stare bruning holes through you. Rus was giving small, light love bites along your neck, his hands creeping around your torso to play with your tits,his long fingers easily caging them. You had never felt so aroused in your life, so well and thoroughly stimulated. 

That's what you thought, and that thought was instantly shattered when you felt something warm, gelatinous starting to massage your clit. It was impossible to keep your voice down, moaning and keening as Sans licked you expertly. With his fingers plunding into you and curling into your g-spot you were already so close to cumming. 

You couldn't help but wonder how Sans would feel like. You couldn't see what size he was, but he was shorter than Rus. And you knew that he had a pretty formidable cock, pierced with few rings down the underside of his shaft. You could feel them digging into your back every moment, grinding desperately to you. 

Your train of thought was yet again interrupted by Sans, when he growled roughly against you, like he too was getting impatient. You had no idea how heat felt, but it must have been torture. With a grunt he added a third finger inside you and sped up his administrations and you couldn't hold on anymore, coming apart with a broken whimpers, Rus squeezing your nipples with his hard fingers, his grip like a vise. 

**”Turn her around, I wanna see her choking on your cock.”** Sans barked an order and Rus handled your limp body like it weighed nothing, clicking your hands free momentarily from the bed and back together in the cuffs. 

You could hardly keep on your fours, legs trembling, the ropes starting to cut off your circulation a little bit. You could hold on for a while longer, you didn't want to beg for release from them yet. 

You fumbled around, trying to manage to open Rus' pants and free his twitching member. Sans was raking his fingers across your back and ass, appreciating the exposed skin. When you seemed to be taking too much time getting his brother free from the confines of his boxers, you felt him swat your ass hard, making you yelp. 

**”Get to it already.”**

”I'm trying.. aAAh!” With a thrust you weren't expecting at all, he forced his cock inside you, making you squel with surprise. Oh God, it felt so good, so warm and hard, he was definitely pretty girthy, and with another aggressive pump you could feel the ridges under his dick, maybe he had piercings too? You couldn't be sure. 

Sans grabbed your hair viciously, making you yelp again and pushed your mouth against Rus' cock, and it slid forcefully into your already open mouth. The slight taste of salt and clementines invaded your tastebuds and you sucked. Shit, you didn't think Rus had ever been this hard. You were lucky your gag reflex wasn't that bad, as he bucked his hips with a moan, hitting the back of your throath unapologetically. For such a lazy dude he sure loved to push your limits with blowjobs. 

With an appreciative growl Sans let up his hold on your hair, starting a deep and punishing rhythm aiming his thrusts just right. You were a mewling, drooling mess, letting Rus fuck your mouth, just trying to keep breathing through it.

Before long you were already aching for another orgasm, trying hard to match Sans' fervor, toes curling and desperate for release. Sans was cursing up a storm against your back, you could feel the sweat dripping from his skull on your skin, his sharp, sharklike teeth leaving lovebites along your whole back. You didn't even flich if his teeth pierced your skin, and he was quick to lap up the blood that probably pooled to the surface. 

He could feel you tensing and your pelvic muscles starting to convulse as another orgasm ripped through you and he wrapped his arms around your middle, face pressed to your back, growling helpless **”fuck, fuck, fuck fuck”** curses against you, fucking you through the bursts of pleasure. It was obvious he came too, since there was so much liquids streaming down your thighs. But he certainly wasn't stopping and you were starting to get a bit overstimulated. 

And your legs were aching by now.

You whined with Rus' cock still in your mouth, trying to tap his femur desperately and to your relief he noticed, pulling out and cooing; ”Fuckin' hell Darlin'.. ya look gorgeous..”

”.. my legs, please..” you pleaded after gathering your breath a bit, pulling at the blindfold.

”Ahh.. bro, would'ya..” 

Finally Sans pulled out and grabbed onto the ropes binding your legs and just.. effortlessly ripped them off, snapping the cords like they were nothing to him. Damn, you didn't realise he was that strong. 

With your legs now freed, you stretched them out, feeling them shaking like leaves. Oh shit, circulation was starting to come back and with that, the intense pain. Rus freed you from the handcuffs and the blindfold that had slid down to hang around your neck. 

Seeing them both look at you with such fire in their eyesockets made you blush dark red, having the blindfold had weirdly enough acted like a safeguard against the strange situation, but now you were quite literally face to face with it. Both of them were wrecks, and so were you, both of the brothers sporting similarly bright flushes on their faces, panting, sweaty. You hazarded a glance at Sans' crotch, his member twitching with exitement at the attention. So he wasn't pierced after all, but he had ridges that ran along the underside of his magic formed cock. 

A quick glance to Rus. He wasn't done either, his member wet with your saliva and still as rock hard as before. 

**”On his lap, now.”** Sans bit out, already pushing you to Rus, making you straddle his femurs and he pulled you lovingly to his sternum, teeth meeting your lips in a passionate kiss, slipping his tongue inside. 

You felt Sans lifting you by your hips, guiding you down Rus' shaft, impaling you on the long member. Moaning into the kiss you ground down to him, tired but more than happy to satisfy your boyfriend. 

Sans snaked his hands around you, grabbing you breasts and rolling the nipples, clearly fascinated with them. He was nuzzling his face into your neck, licking your skin and growling softly. You wondered briefly how long a heat went on but the thought broke into a trembling breath when you felt his cock poke your labia, sliding against his brothers, that was still moving languidly inside. 

He couldn't mean he would.. 

”.. Sans! I can't take you both!” you whined, incredulous. 

**”You can and you will.”** his voice didn't leave any room for discussion but you fidgeted nervously against Rus.

”No, I'll split!” 

”Easy, Darlin'. Our junk is made with magic, ya'll be fine. Trust us.” Rus' deep voice murmured against your neck, arousal pooling with fear in your gut. 

Sans took that as good as a ”go” and started to push into you, alongside Rus. You felt so full, ready to burst, but not badly so, as he bottomed out. You were breathing erraticly, still fearing for something to go wrong, but nothing did, everything was good, you could relax. 

**”See, it's fine, good girl.. ahh, you're so fucking tight..”**

They started up a syncroniced pace, plunging deep inside, their combined cocks stroking every possible spot inside you and you were close to just completely losing your mind, gasping and panting, not that they kept their voices down either, growling and grunting with the effort and pleasure. 

Rus was first to lose the battle and he came with a groan, his fingers digging into your hips, teeth into your shoulder, his cum flowing down to the beadspread, Sans on the other hand was _still_ going, he seemed to just gain more energy from somewhere, aggressively pounding into you, making you hang on to Rus' neck for dear life. 

He was jackhammering to you so forcefully that you simply couldn't help the fast approaching orgasm that made tears stream down your face, and he just kept fucking you through the waves. You were completely listless by the time he finally _finally_ came and collapsed on your back. 

The bed was a mess. You were a mess. The brothers were a mess. The smell of sex in the room was so strong it would've knocked lesser creatures from their feet. 

”I.. I need to take a shower, fuck that was .. something else.” you wrinkled your nose, gingerly touching your aching pussy. Your fingers were coated into the combined mess of both of their cum and your slick instantly. You shivered.

**”You think I'm done? So easily? Mwahaha – think again, human.”** You could feel Sans' malicious grin against the skin of your back. 

”You can't be fucking serious...” 

”'m pretty sure he is. His heats last for a week.” Rus sighed and you could feel your heart plummet to your stomach.

This was gonna be one long-ass week. The room filled with venomous curses that you spewed out vigorously, making Rus bark out a genuine laugh. 

”I hate you both.”

**”No you don't.”**

You didn't, it was true.

**Author's Note:**

> Find me in the tumblr void  
> [The pit](https://hibernalbeast.tumblr.com/)


End file.
